Module 3: Weather, Loading, and Performance

______ is what you expect and ______ is what you get

1) Climate
2) Weather

What is the troposphere?

The lowest layer in the atmosphere, which is characterized as a region where, in general, temperature decreases with altitude. This is also the region where sUAS can operate

On average, the environmental temperature within the troposphere decreases ______ °F per ______ ft

1) 3.5
2) 1000

What do meteorologists use as the standard sea-level value of temperature?

+15°C

What do aviators use as the standard sea-level value of pressure?

29.92" of Mercury

What do meteorologists use as the standard sea-level value of density?

1.225 kg/m3

What is the ABL?

Atmospheric Boundary Layer; the lowest layer of the troposphere that’s strongly influenced by the Earth’s surface

Variations in pressure can be readily visualized by the inspection ______, which are lines that connect locations of equal pressure

Isobars

What are the characteristics of Pressure Gradient Force?

• A force exerted over an area

• When a difference in pressure exists over a distance, a net force exists

• A net or unbalanced force brings about an acceleration

What are the characteristics of Coriolis Force?

• An effect that moves air parcels to the right

• A consequence of inertia showcased on rotating Earth

What are the characteristics of friction?

• Creates surface winds that flow clockwise and outward around areas of high pressure

• Creates surface winds that flow counterclockwise and inward around areas of low pressure

• Slows the wind driven by the PGF

• Decreases the effect of the Coriolis Force

• Creates a dynamic where the PGF remains stronger than the Coriolis Force

• A force that retards forward motion

Flow aloft can be constructed from the balance between which two drivers?

1) Pressure Gradient Force
2) Coriolis Force

How can a remote Pilot in Command (PIC) estimate the speed and direction of surface wind?

Inspecting surface pressure charts

What does Buys Ballot’s law state?

With your back to the wind, low pressure will be to your left while high pressure will be to your right

What is the key to keeping all of the different types of local circulations straight?

Remember that wind is always described by the direction it comes from

When flying in a coastal region, a UAS pilot should expect a breeze to commence several hours ______ sunrise

After

When flying in a coastal region, a UAS pilot should expect wind speeds as great as 5-10 knots by ______

Midafternoon

When flying in a coastal region, a UAS pilot can expect a robust sea breeze to extend up to ______ ft in altitude

1000

What factor determines the strength of mountain and valley breezes

Solar heating

Valley breezes are most prevalent during the ______ season while mountain breezes are more common during the ______ season

1) Warm
2) Cold

When wind is channeled through areas, such as a narrow valley or between tall buildings or structures, what should be expected of wind speed?

An increase

What is turbulence?

Temporary fluctuations, or gustiness, that are superimposed on the sustained wind

How is thermal turbulence created?

Through the uneven heating of the Earth’s surface, which causes pockets of warm air to rise

What three aspects influence the intensity of thermal turbulence?

1) Surface type: Materials such as asphalt, rock, and sand heat up faster than grass or water, creating stronger temperature contrasts
2) Time of day: Turbulence typically peaks during midday and afternoon when solar radiation is strongest
3) Atmospheric conditions: Higher temperatures and unstable air masses can intensify updrafts/downdrafts

How is mechanical turbulence created?

By wind shear, which are abrupt changes in the speed or direction of the flow, brought about by the force of the drag

What three aspects influence the intensity of mechanical turbulence?

1) Differences in wind speed and direction: Stronger winds that flow in opposite horizontal directions generally create more severe turbulence
2) Surface roughness and density: Irregular terrain or areas with dense obstacles or obstructions like urban environments cause greater disruption than smooth surfaces like flat oceans

3) Air stability: Unstable air allows eddies to grow larger and more chaotic, while stable air causes them to dissipate more slowly

Thermal turbulence can be considered ______ while mechanical turbulence can be considered ______

1) Vertical turbulence
2) Horizontal turbulence

When should stronger wind speeds be expected?

During daytime hours and with an increase in altitude

How are stratus clouds characterized?

Gray and layered in appearance, typically covering the entire sky

How are cumulus clouds characterized?

Distinct, puffy clouds that are more vertically developed, often appearing like cotton balls in the sky with flat bases

______ is associated with precipitation that fall from stratus or cumulus clouds

Nimbus

What are the six sky descriptions that are used based on the fraction of the sky covered by clouds?

1) Clear (CLR)
2) Few clouds (FEW)
3) Scattered (SCT) or partly cloudly
4) Broken (BKN) or cloudy
5) Overcast (OVC)
6) Sky obscured

How does radiation fog occur?

Brought about by the cooling of air adjacent to the ground

How does ice fog occur?

Formed when the underlying surface that cool air is flowing over is sufficiently cold

How does steam fog occur?

The air mass becomes saturated when a warm and moist underlying surface evaporates

How does frontal fog occur?

Occurs when warm rain falls into layer of cold and moist air

A visibility of at least ______, as observed from the Control Station (CS), is required throughout the duration of flight operations

3 statute miles

If a remote pilot or visual observer cannot identify objects at a known distance or at distances marked on a map, what should the remote pilot do?

Not conduct flight operations

What are the two elements that make ice formation possible?

1) An environment with visible moisture
2) UAS’ surface temperature is 0°C or below

What are four adverse effects that icing causes in respects to a UAS’ performance?

1) Decrease in lift
2) Decrease in thrust
3) Increase in drag
4) Increase in weight

What is an air mass?

A large volume of air with horizontally consistent moisture and temperature characteristics

What are the three classifications used for temperature?

1) Tropical (warm)

2) Polar (cool)
3) Arctic (cold)

What are the two classifications used for humidity?

1) Continental (dry)
2) Maritime (moist)

Stratiform and cirrus clouds can extend several hundred miles in advanced of the surface front and foretell a frontal passage several ______ in advance

Days

In the middle latitudes, winds ahead of a cold front are typically ______ and, while they become stronger and gustier during passage, they turn more ______ following frontal passage

1) Southerly
2) Northerly

What is an occluded front?

A fast-moving cold front, that catches a warm front, forming an occlusion with the boundary

If the temperature of the air behind the overtaking cold front is not as cool as the air ahead of the overtaken warm front, the occluded front is referred to as a ______

Warm occlusion

If the temperature of the air behind the overtaking cold front is below the temperature of the cool air ahead of the overtaken warm front, the occluded front is referred to as a ______

Cold occlusion

What are the three stages of a thunderstorm life cycle?

1) Cumulus stage
2) Mature stage
3) Dissipating stage

Operations should not be planned when lightning is forecast within ______

15 miles

If caught by an approaching storm, what two things should be done?

1) Either seek shelter in a completely enclosed structure or in a fully enclosed metal vehicle
2) Avoid residing next to tall objects or lying on the ground

What are surface analysis charts?

Provide a big picture view of the weather, illustrating high and low-pressure areas and along with surface fronts

How often are surface analysis charts reported?

Every 3 hours

What is a METAR?

Aviation Routine Weather Report: Provides surface observations at select airports

How often are METARs reported?

Every hour

What eleven details do METARs include?

1) Type of report

2) Airport identifier; “K” stands for continental United States
3) Date and time in Zulu
4) Corrected; “C-O-R” refers to the METAR being a corrected automated report

5) Wind direction and speed
6) Visibility
7) Present weather

8) Sky condition
9) Temperature and dew point
10) Altimeter setting/barometric pressure

What is a TAF?

Terminal Aerodrome Forecast: Concisely states expected conditions at select

TAFs are valid for a ______ time period and is updated ______ times a day

1) 24 or 30-hour time period

2) Four

At what times are TAFs updated?

0000Z, 0600Z, 1200Z, and 1800Z

What is a Flight Service?

An alternative way to obtain weather information via www.1800wxbrief.com

Telephone-based Flight Service resources are for ______ only

Manned aircraft pilots

What is an ASOS?

Automated Surface Observing System (ASOS): Consists of requisite sensors, computers, and communication systems to automatically record and disseminate atmospheric conditions continuously at one-minute intervals

What are the ten details that an ASOS detects?

1) Cloud coverage
2) Ambient temperature
3) Wind direction
4) Visibility
5) Significant changes to weather
6) Obstructions to visibility
7) Precipitation
8) Wind speed
9) Cloud height
10) Pressure

What is an AWOS?

Consists of various sensors, a processor, a computer-generated voice subsystem, and a transmitter to broadcast weather data

What is a SIGMET?

Significant Meteorological Information: Inflight weather advisories for significant meteorological hazards covering an area of at least 3,000 square miles

What are the four types of potentially hazardous weather?

1) Severe icing
2) Severe or extreme turbulence
3) Dust storms and/or sand storms lowering visibilities to less than three miles
4) Volcanic ash

What are three instances when convective SIGMETs are issued?

1) Line of thunderstorms at least 60 miles long with wind gusts greater than 50 knots, hail at the surface greater than or equal to ¾ inch in diameter, or tornadoes

2) Area of thunderstorms covering at least 40% of the area concerned and exhibiting a very strong radar reflectivity or a significant satellite or lightning signature
3) Embedded and squall lines of severe thunderstorms are expected to occur for more than 30 minutes

What are seven performance factors that are crucial for aircraft?

1) Speed

2) Range
3) Payload capacity
4) Maneuverability
5) Rate of climb
6) Service ceiling
7) Endurance

What are eight flight limitation factors of a UAS?

1) Maximum airspeed
2) Altitude
3) Bank angle
4) Climb/descent rates
5) Payload capacity
6) Vehicle gross weight
7) Wind speed
8) Ambient temperature

What is dead reckoning?

A navigation technique based on estimating the current position using previously determined positions, along with known or estimated speeds and direction of travel

Who is responsible for verifying the correct W&B before any sUAS flight?

The pilot

If the center of gravity (CG) is not within the manufacturer’s allowable limits…

It’s necessary to relocate or shed some weight

Increasing the weight of a fixed-wing aircraft will result in the wing operating at a ______ AOA, producing more induced drag

Higher

Load factor ______ during maneuvers involving acceleration or direction changes, such as turns and climbs

Increases

______ load factors impose greater stress on the aircraft’s structure, requiring it to be designed and built to withstand these forces without compromising safety

Higher

What is stall?

Occurs when the AOA of an aircraft’s wing exceeds the critical angle of attack

What is Angle of Attack (AOA)

The angle between the chord line of an aircraft’s wing and the direction of the oncoming airflow

What is Critical Angle of Attack?

The angle at which the airflow over the wing separates, causing a significant decrease in lift and drag

What is stall speed?

The lowest airspeed at which the wings of an aircraft can still generate enough life to support its weight

What three aspects affects an aircraft’s stall speed?

1) Angle of attack
2) Weight
3) Configuration

Generally, stall speed ______ with an increase in aircraft weight and ______ with a decrease in weight

1) Increases
2) Decreases

Stall speeds with increase in proportion to the square root of ______

Load factor

A fixed-wing sUAS should be launched and landed…

Into the wind

Wind velocity ______ with altitude at a logarithmic rate and is based on the height of obstructions on the ground’s surface

Increase

One should always anticipate wind velocities at 400 ft AGL to be ______ as much as they are measured near the surface

Twice

Air density ______ with increasing temperature

Decreases

Increasing temperature and humidity, or ______ pressure, decreases air density

Decreasing

What three factors influence high density altitude?

1) Humidity
2) Elevation
3) Temperature

______ air can hold more water vapor, while ______ air can hold less

1) Warm
2) Colder

What is the relationship between aircraft performance and humidity conditions?

In high humidity conditions, performances decreases. In low humidity conditions, performance increases. Inverse relationship

Most humans and electronic devices operate optimally within ______ degrees Fahrenheit and with humidity below ______ %

1) 68 to 75
2) 55